1. Technical Field
This invention generally relates to an inflatable lining for footwear, and specifically to an inflatable inner sole with protective and comfortable coatings and surrounds and methods of manufacture.
2. State of the Art
Inner soles have been provided for shoes and boots which are formed of a compressible, elastic material such as cellular plastic foams, foam rubber, etc. These inner soles have provided only limited shock absorbency, resulting in little or no significant improvement in wearer comfort.
Sport socks are also available for hikers and runners which have a double layer of fabric on the undersurface of the sock in an attempt to prevent formation of blisters.
In some foot apparel, notably in ski boots, an outer shell is molded from plastic and is lined with an inner shoe. Adjustment has been made to the tightness of the outer shell and air bags have been provided across the instep region of the shoe, and elsewhere, and have been provided with an air pump to pressurize the air bags, thus forcing the foot against the sole and creating a snugness of the fit of the ski boot.
A water-filled inner sole for shoes has recently been marketed under the trade name “Walk On Water”. While this is an attempt to increase wearer comfort, water is heavy, non-compressible and the inner sole cannot be adjusted for firmness, and cannot provide shock absorbency. Additionally, water is unsuited for use in freezing climates. Also, a leak will wet the inside of the footwear, and this inner sole is not breathable.
Another recently marketed innovation is that disclosed in U.S. Pat. Nos. 4,183,156; 4,340,626 and 4,817,304 in which an inflatable inner sole or sole insert is permanently inflated with halogenated hydrocarbon gases. Since it is impossible to preclude diffusion of gases through the plastic, the inflatable insert or inner sole is acknowledged to experience a rapid increase in pressure shortly after manufacture, followed by a slowly declining pressure, thus failing to provide a stable condition. The pressure of the inflatable member also can not be adjusted by the wearer for varying conditions of use and comfort.